As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLOOR NUTPLATE CAME LOOSE WHILE INSTALLING A SCREW AND DAMAGED THE SUPPORT RIB. DURING THE INSTALLATION OF A LITTER LOADING ATTACHMENT SCREW INTO A NUTPLATE IN FLOOR IN CABIN AREA, LT SIDE OF ACFT, RIVETS RETAINING THE NUTPLATE SHEARED. THE NUTPLATE SUBSEQUENTLY SPUN ABOUT THE ATTACHING SCREW, DAMAGING THE OEM SUPPORT RIB.